Examples of perpendicular lines

1. Are these straight lines perpendicular?

If the lines intersect at 90 degrees then they are perpendicular

The formula for each line is:

$y = 2x + 4$

And $y=-1/2x-1$

And $y=mx+c$ where m is the gradient

The test for perpendicular

$m_1\times\m_2=-1$

$2\times-1//2=?$

$2\times-1//2=-1$

Yes these lines are perpendicular.